A Chemical Theory of Spontaneous Generation 151 



exception, has been questioned [9]. It is now clear that a critical detail in forming 

 peptides by heating amino acids is not to heat them singly, as in the procedures 

 reported in virtually all of the discouraging early literature, but to heat them in 

 concert. 



For these results, the dicarboxylic acids, glutamic acid and aspartic acid, are 

 of particular significance. Glutamic acid heated alone yields the inner lactam : 



COOH 



HoNCH CH2 CH, 



"I II 



CH, " = C HC— COOH 



I \ / 



CH, NH 



I 

 COOH 



but when heated with glycine, which forms a linear polyglycine, it yields a polymer 

 containing typically 20% of glutamic acid. The polymer gives rich infra-red 

 indication of being a linear peptide and other evidence as well. 



As Kovacs suggested earUer [11], polyaspartic acid is a polyimide which hydro- 

 lyses to a true peptide under alkaline conditions. This structural interpretation 

 has been substantiated in our laboratory (A. Vegotsky, K. Harada & S. W. Fox, 

 unpublished experiments) with the aid of infra-red studies. 



These experimental results with glutamic acid and aspartic acid are significant 

 in that they designate principles whereby one can visualize how a variegated 

 peptide such as a protein might form under primitive thermal conditions, despite 

 the negative indications from the literature. In view of the concept of a yet highly 

 limited evolution of protein molectiles [12, 13] the fact that most proteins are 

 composed of at least one-fifth dicarboxyUc amino acid residues is more under- 

 standable. Another feature is that these reactions need not be solid reactions in- 

 asmuch as the lactam of glutamic acid, pyrroUdonecarboxylic acid, is Uquid at 

 the temperatures employed (in the range of 160-180°). A Uquid state also results 

 from phosphoric acid, inclusion of which has been found to faciUtate many of 

 the reactions studied (K. Harada & S. W. Fox, unpubhshed experiments). 



The thermal pathways of Fig. 3 are striking in their similarity to the sequences 

 involved in the early stages of a generalized biosynthesis for all organisms. 

 Obviously there are differences, but the compounds and their order of appear- 

 ance in the thermal picture resemble closely the substances and sequences of 

 anabolism. Another perspective for viewing this parallelism is provided by the 

 biogenetic law. If one accepts the concept that the development of an organism 

 reflects its evolutionary history, he should then expect that this principle would 

 be reducible to the chemical level. In the depiction of Fig. 3, this requirement 

 appears to be met. 



Not only have the thermal pathways been fotmd to imitate the anaboUc path- 

 ways. It is now possible to point to features that were first uncovered by thermal 

 studies, and then disclosed by more conventional biochemical experimentation. 



